text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Generic HDLC support routines for Linux
   * Cisco HDLC support
   *
   * Copyright (C) 2000 - 2006 Krzysztof Halasa <khc@pm.waw.pl>
   */
  
  #include <linux/errno.h>
  #include <linux/hdlc.h>
  #include <linux/if_arp.h>
  #include <linux/inetdevice.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/pkt_sched.h>
  #include <linux/poll.h>
  #include <linux/rtnetlink.h>
  #include <linux/skbuff.h>
  
  #undef DEBUG_HARD_HEADER
  
  #define CISCO_MULTICAST		0x8F	/* Cisco multicast address */
  #define CISCO_UNICAST		0x0F	/* Cisco unicast address */
  #define CISCO_KEEPALIVE		0x8035	/* Cisco keepalive protocol */
  #define CISCO_SYS_INFO		0x2000	/* Cisco interface/system info */
  #define CISCO_ADDR_REQ		0	/* Cisco address request */
  #define CISCO_ADDR_REPLY	1	/* Cisco address reply */
  #define CISCO_KEEPALIVE_REQ	2	/* Cisco keepalive request */
  
  struct hdlc_header {
  	u8 address;
  	u8 control;
  	__be16 protocol;
  } __packed;
  
  struct cisco_packet {
  	__be32 type;		/* code */
  	__be32 par1;
  	__be32 par2;
  	__be16 rel;		/* reliability */
  	__be32 time;
  } __packed;
  #define	CISCO_PACKET_LEN	18
  #define	CISCO_BIG_PACKET_LEN	20
  
  struct cisco_state {
  	cisco_proto settings;
  
  	struct timer_list timer;
  	struct net_device *dev;
  	spinlock_t lock;
  	unsigned long last_poll;
  	int up;
  	u32 txseq; /* TX sequence number, 0 = none */
  	u32 rxseq; /* RX sequence number */
  };
  
  static int cisco_ioctl(struct net_device *dev, struct if_settings *ifs);
  
  static inline struct cisco_state *state(hdlc_device *hdlc)
  {
  	return (struct cisco_state *)hdlc->state;
  }
  
  static int cisco_hard_header(struct sk_buff *skb, struct net_device *dev,
  			     u16 type, const void *daddr, const void *saddr,
  			     unsigned int len)
  {
  	struct hdlc_header *data;
  #ifdef DEBUG_HARD_HEADER
  	netdev_dbg(dev, "%s called\n", __func__);
  #endif
  
  	skb_push(skb, sizeof(struct hdlc_header));
  	data = (struct hdlc_header *)skb->data;
  	if (type == CISCO_KEEPALIVE)
  		data->address = CISCO_MULTICAST;
  	else
  		data->address = CISCO_UNICAST;
  	data->control = 0;
  	data->protocol = htons(type);
  
  	return sizeof(struct hdlc_header);
  }
  
  static void cisco_keepalive_send(struct net_device *dev, u32 type,
  				 __be32 par1, __be32 par2)
  {
  	struct sk_buff *skb;
  	struct cisco_packet *data;
  
  	skb = dev_alloc_skb(sizeof(struct hdlc_header) +
  			    sizeof(struct cisco_packet));
  	if (!skb)
  		return;
  
  	skb_reserve(skb, 4);
  	cisco_hard_header(skb, dev, CISCO_KEEPALIVE, NULL, NULL, 0);
  	data = (struct cisco_packet *)(skb->data + 4);
  
  	data->type = htonl(type);
  	data->par1 = par1;
  	data->par2 = par2;
  	data->rel = cpu_to_be16(0xFFFF);
  	/* we will need do_div here if 1000 % HZ != 0 */
  	data->time = htonl((jiffies - INITIAL_JIFFIES) * (1000 / HZ));
  
  	skb_put(skb, sizeof(struct cisco_packet));
  	skb->priority = TC_PRIO_CONTROL;
  	skb->dev = dev;
  	skb->protocol = htons(ETH_P_HDLC);
  	skb_reset_network_header(skb);
  
  	dev_queue_xmit(skb);
  }
  
  static __be16 cisco_type_trans(struct sk_buff *skb, struct net_device *dev)
  {
  	struct hdlc_header *data = (struct hdlc_header *)skb->data;
  
  	if (skb->len < sizeof(struct hdlc_header))
  		return cpu_to_be16(ETH_P_HDLC);
  
  	if (data->address != CISCO_MULTICAST &&
  	    data->address != CISCO_UNICAST)
  		return cpu_to_be16(ETH_P_HDLC);
  
  	switch (data->protocol) {
  	case cpu_to_be16(ETH_P_IP):
  	case cpu_to_be16(ETH_P_IPX):
  	case cpu_to_be16(ETH_P_IPV6):
  		skb_pull(skb, sizeof(struct hdlc_header));
  		return data->protocol;
  	default:
  		return cpu_to_be16(ETH_P_HDLC);
  	}
  }
  
  static int cisco_rx(struct sk_buff *skb)
  {
  	struct net_device *dev = skb->dev;
  	hdlc_device *hdlc = dev_to_hdlc(dev);
  	struct cisco_state *st = state(hdlc);
  	struct hdlc_header *data = (struct hdlc_header *)skb->data;
  	struct cisco_packet *cisco_data;
  	struct in_device *in_dev;
  	__be32 addr, mask;
  	u32 ack;
  
  	if (skb->len < sizeof(struct hdlc_header))
  		goto rx_error;
  
  	if (data->address != CISCO_MULTICAST &&
  	    data->address != CISCO_UNICAST)
  		goto rx_error;
  
  	switch (ntohs(data->protocol)) {
  	case CISCO_SYS_INFO:
  		/* Packet is not needed, drop it. */
  		dev_kfree_skb_any(skb);
  		return NET_RX_SUCCESS;
  
  	case CISCO_KEEPALIVE:
  		if ((skb->len != sizeof(struct hdlc_header) +
  		     CISCO_PACKET_LEN) &&
  		    (skb->len != sizeof(struct hdlc_header) +
  		     CISCO_BIG_PACKET_LEN)) {
  			netdev_info(dev, "Invalid length of Cisco control packet (%d bytes)\n",
  				    skb->len);
  			goto rx_error;
  		}
  
  		cisco_data = (struct cisco_packet *)(skb->data + sizeof
  						    (struct hdlc_header));
  
  		switch (ntohl(cisco_data->type)) {
  		case CISCO_ADDR_REQ: /* Stolen from syncppp.c :-) */
  			rcu_read_lock();
  			in_dev = __in_dev_get_rcu(dev);
  			addr = 0;
  			mask = ~cpu_to_be32(0); /* is the mask correct? */
  
  			if (in_dev != NULL) {
  				const struct in_ifaddr *ifa;
  
  				in_dev_for_each_ifa_rcu(ifa, in_dev) {
  					if (strcmp(dev->name,
  						   ifa->ifa_label) == 0) {
  						addr = ifa->ifa_local;
  						mask = ifa->ifa_mask;
  						break;
  					}
  				}
  
  				cisco_keepalive_send(dev, CISCO_ADDR_REPLY,
  						     addr, mask);
  			}
  			rcu_read_unlock();
  			dev_kfree_skb_any(skb);
  			return NET_RX_SUCCESS;
  
  		case CISCO_ADDR_REPLY:
  			netdev_info(dev, "Unexpected Cisco IP address reply\n");
  			goto rx_error;
  
  		case CISCO_KEEPALIVE_REQ:
  			spin_lock(&st->lock);
  			st->rxseq = ntohl(cisco_data->par1);
  			ack = ntohl(cisco_data->par2);
  			if (ack && (ack == st->txseq ||
  				    /* our current REQ may be in transit */
  				    ack == st->txseq - 1)) {
  				st->last_poll = jiffies;
  				if (!st->up) {
  					u32 sec, min, hrs, days;
  
  					sec = ntohl(cisco_data->time) / 1000;
  					min = sec / 60; sec -= min * 60;
  					hrs = min / 60; min -= hrs * 60;
  					days = hrs / 24; hrs -= days * 24;
  					netdev_info(dev, "Link up (peer uptime %ud%uh%um%us)\n",
  						    days, hrs, min, sec);
  					netif_dormant_off(dev);
  					st->up = 1;
  				}
  			}
  			spin_unlock(&st->lock);
  
  			dev_kfree_skb_any(skb);
  			return NET_RX_SUCCESS;
  		} /* switch (keepalive type) */
  	} /* switch (protocol) */
  
  	netdev_info(dev, "Unsupported protocol %x\n", ntohs(data->protocol));
  	dev_kfree_skb_any(skb);
  	return NET_RX_DROP;
  
  rx_error:
  	dev->stats.rx_errors++; /* Mark error */
  	dev_kfree_skb_any(skb);
  	return NET_RX_DROP;
  }
  
  static void cisco_timer(struct timer_list *t)
  {
  	struct cisco_state *st = from_timer(st, t, timer);
  	struct net_device *dev = st->dev;
  
  	spin_lock(&st->lock);
  	if (st->up &&
  	    time_after(jiffies, st->last_poll + st->settings.timeout * HZ)) {
  		st->up = 0;
  		netdev_info(dev, "Link down\n");
  		netif_dormant_on(dev);
  	}
  
  	cisco_keepalive_send(dev, CISCO_KEEPALIVE_REQ, htonl(++st->txseq),
  			     htonl(st->rxseq));
  	spin_unlock(&st->lock);
  
  	st->timer.expires = jiffies + st->settings.interval * HZ;
  	add_timer(&st->timer);
  }
  
  static void cisco_start(struct net_device *dev)
  {
  	hdlc_device *hdlc = dev_to_hdlc(dev);
  	struct cisco_state *st = state(hdlc);
  	unsigned long flags;
  
  	spin_lock_irqsave(&st->lock, flags);
  	st->up = st->txseq = st->rxseq = 0;
  	spin_unlock_irqrestore(&st->lock, flags);
  
  	st->dev = dev;
  	timer_setup(&st->timer, cisco_timer, 0);
  	st->timer.expires = jiffies + HZ; /* First poll after 1 s */
  	add_timer(&st->timer);
  }
  
  static void cisco_stop(struct net_device *dev)
  {
  	hdlc_device *hdlc = dev_to_hdlc(dev);
  	struct cisco_state *st = state(hdlc);
  	unsigned long flags;
  
  	del_timer_sync(&st->timer);
  
  	spin_lock_irqsave(&st->lock, flags);
  	netif_dormant_on(dev);
  	st->up = st->txseq = 0;
  	spin_unlock_irqrestore(&st->lock, flags);
  }
  
  static struct hdlc_proto proto = {
  	.start		= cisco_start,
  	.stop		= cisco_stop,
  	.type_trans	= cisco_type_trans,
  	.ioctl		= cisco_ioctl,
  	.netif_rx	= cisco_rx,
  	.module		= THIS_MODULE,
  };
  
  static const struct header_ops cisco_header_ops = {
  	.create = cisco_hard_header,
  };
  
  static int cisco_ioctl(struct net_device *dev, struct if_settings *ifs)
  {
  	cisco_proto __user *cisco_s = ifs->ifs_ifsu.cisco;
  	const size_t size = sizeof(cisco_proto);
  	cisco_proto new_settings;
  	hdlc_device *hdlc = dev_to_hdlc(dev);
  	int result;
  
  	switch (ifs->type) {
  	case IF_GET_PROTO:
  		if (dev_to_hdlc(dev)->proto != &proto)
  			return -EINVAL;
  		ifs->type = IF_PROTO_CISCO;
  		if (ifs->size < size) {
  			ifs->size = size; /* data size wanted */
  			return -ENOBUFS;
  		}
  		if (copy_to_user(cisco_s, &state(hdlc)->settings, size))
  			return -EFAULT;
  		return 0;
  
  	case IF_PROTO_CISCO:
  		if (!capable(CAP_NET_ADMIN))
  			return -EPERM;
  
  		if (dev->flags & IFF_UP)
  			return -EBUSY;
  
  		if (copy_from_user(&new_settings, cisco_s, size))
  			return -EFAULT;
  
  		if (new_settings.interval < 1 ||
  		    new_settings.timeout < 2)
  			return -EINVAL;
  
  		result = hdlc->attach(dev, ENCODING_NRZ,
  				      PARITY_CRC16_PR1_CCITT);
  		if (result)
  			return result;
  
  		result = attach_hdlc_protocol(dev, &proto,
  					      sizeof(struct cisco_state));
  		if (result)
  			return result;
  
  		memcpy(&state(hdlc)->settings, &new_settings, size);
  		spin_lock_init(&state(hdlc)->lock);
  		dev->header_ops = &cisco_header_ops;
  		dev->hard_header_len = sizeof(struct hdlc_header);
  		dev->type = ARPHRD_CISCO;
  		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
  		netif_dormant_on(dev);
  		return 0;
  	}
  
  	return -EINVAL;
  }
  
  static int __init hdlc_cisco_init(void)
  {
  	register_hdlc_protocol(&proto);
  	return 0;
  }
  
  static void __exit hdlc_cisco_exit(void)
  {
  	unregister_hdlc_protocol(&proto);
  }
  
  module_init(hdlc_cisco_init);
  module_exit(hdlc_cisco_exit);
  
  MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
  MODULE_DESCRIPTION("Cisco HDLC protocol support for generic HDLC");
  MODULE_LICENSE("GPL v2");
  